1. Technical Field
The present invention relates in general to a disk drive apparatus such as a hard disk drive, and in particular, to a technique for fast writing or reading data into or from an alternative sector if a data track of a recording medium contains a defective sector and more particularly, to a technique suitable for handling audio-visual data.
2. Description of the Related Art
A hard disk drive is one of the most popular external storage devices for a computer. As is well known, the surface of a hard disk (also called a xe2x80x9cmagnetic diskxe2x80x9d), which is the recording medium in the hard disk drive, is divided into circular tracks and each track is radially divided into sectors, which are the smallest storage units on the disk. The tracks near the edge of the hard disk provide a higher line storage density than tracks nearer the center. With the xe2x80x9cZone-Bit Recordingxe2x80x9d scheme, which is a today""s dominating data recording technique for hard disks, all the tracks are grouped into zones so that each zone has a constant line storage density. The length of each sector is typically 512 bytes, so tracks nearer the edge of the hard disk contain more sectors.
Tracks are not necessarily in good condition. A track may contain a defective sector in which data cannot be written or read due to a flaw or dust. If a defective sector is detected in the manufacturing process of a hard disk, an alternative sector is allotted in place of the defective sector. A defective sector may not always occur in the manufacturing process. It may occur in use after delivery. Also in such a case, an alternative sector is allotted in place of the defective sector. The allotment of an alternative sector in a manufacturing process is called xe2x80x9cassignmentxe2x80x9d and the allotment of an alternative sector after delivery is called xe2x80x9cre-assignment.xe2x80x9d
A group of sectors to be used as alternative sectors are positioned in a specific area on a hard disk. For example, in a case of the above-described zone-bit recording the alternative sector area may be provided in a specific area in an outer track and an inner track of each zone in the radial direction of the disk. Therefore an alternative sector and an original replaced sector are typically not in the same track. When data stored in the alternative sector is read, the magnetic head actuator of the hard disk drive should perform a seek operation from a track containing the original sector to the inner or outer track in the same zone. Because the seek operation is performed each time data is read from the re-assigned alternative sector, the performance of the hard disk drive momentarily decreases when alternative sectors are successively accessed to read data.
The re-assignment is performed to an alternative sector in the nearest sector area to the defective sector. Therefore, if a major defect occurs in the radially middle of the zone (hereinafter called simply the xe2x80x9cmiddle of a zonexe2x80x9d) and a number of sectors become defective, the re-assignment may be performed to alternative sectors in both of the inner and outer alternative sector area. This requires seek operations between the inner alternative sector and the outer alternative sector, thereby aggravating the momentary performance decrease. Especially when audio/visual data is handled, the momentary performance decrease may lead to a momentary halt of a moving image or a sound skip and therefore should be taken seriously compared to cases where computer data is handled.
Various solutions to the performance decrease due to seek operation have been proposed.
For example, Published Unexamined Patent Application No. 5-66999 proposes a method for storing and managing data recorded in an alternative sector on a hard disk in cache memory of the hard disk apparatus. In the hard disk apparatus, data in the alternative sector is stored and managed in the cache memory, which is fast memory, and when the data is to be read, the data in the cache memory is accessed and read instead of accessing the hard disk which takes much time for an access. Thus the data can be read quickly.
Published Unexamined Patent Application No. 11-232046 discloses a method for reading, in addition to data stored in an alternative sector to be read, data stored in an alternative sector subsequent to an alternative sector and storing the data in memory for alternative sector. With this method, instead of accessing a plurality of alternative sectors separately, data stored in the plurality of sectors are accessed and read at a time, thereby reducing the number of accesses. In addition, because a hard disk takes time of milliseconds for an access whereas the memory allows for access time of nanoseconds, time required for reading data from alternative sectors can be significantly reduced.
For magneto-optical disks, Published Unexamined Patent Application No. 8-167250 discloses an apparatus which allows a defect remedy process to be performed quickly by providing in a disk drive a buffer storage section formed of semiconductor memory as a backup storage for temporarily storing data, besides conventional alternative sectors.
The above-mentioned approaches described in Published Unexamined Patent Applications Nos. 5-66999, 11-232046, and 8-167250 are effective for the reduction of time required for reading data from alternative sectors.
The technology disclosed in Published Unexamined Patent Application No. 5-66999 previously stores all data stored in all alternative sectors of a hard disk in cache memory. Today, this method for storing data stored in all alternative sectors in cache memory is impractical because the storage capacity of recent hard disk devices is enormous.
Published Unexamined Patent Application No. 11-232046 provides the description of reading data in alternative sectors the number of which optimized by the memory device. It, however, does not propose a specific method for optimizing the number of alternative sectors for reading data from the alternative sectors.
The technology disclosed in Published Unexamined Patent Application No. 8-167250 involves the provision of a buffer storage section. However, providing such a new component increases the cost of the product.
Therefore, it is an object of the present invention to provide a method for reading data in alternative sectors faster without providing additional memory for storing data stored in alternative sectors, that is, without adding a new hardware component to a hard disk drive, unlike Published Unexamined Patent Application No. 8-167250.
If a number of defective sectors occur in the middle of a zone and they are within a given distance from one another, data to be written in these sectors are likely to be a series of related items of data and it would be effective to write the data in alternative sectors in one of the inner and outer alternative sector areas in the zone regardless of the distance between each defective sector and the outer or inner alternative sector area. With conventional methods in which defective sectors are re-assigned to inner or outer alternative sectors depending on the distance between a defective sector and the inner or outer area in a zone, a series of related items of data is re-assigned both of the inner and outer alternative sectors in the zone, therefore a seek operation is required between the inner and outer areas of the zone in order to read the data. On the contrary, with the method described earlier in which defective sectors are re-assigned to alternative sectors in one of the inner and outer alternative sector areas if they are within a given distance from one another, the seek operation across the zone is not required in order to read a series of related items of data from the alternative sectors. This means that data can be read faster from the alternative sectors.
While the method has been described with respect to an example in which a number of defective sectors are re-assigned to alternative sectors in one of the inner and outer areas if they are within a given distance from one another, in other words, the physical address of the sectors are successive, the re-assignment may be based on time or the logical addresses of the sectors. That is, when a re-assignment to one alternative sector occurs and then another re-assignment to another alternative sector occurs within a predetermined time, these re-assignments may be performed to alternative sectors in one of the inner and outer areas. If the logical address of a defective sector re-assigned and the logical address of the next defective sector to be re-assigned are adjacent to each other, these re-assignments may be performed to alternative sectors in one of the inner and outer areas.
The present invention solves the problem described earlier by a method for assigning/re-assigning an alternative sector on a zone-bit-recording-scheme recording disk, comprising: a first step of assigning/re-assigning a preceding alternative sector to an alternative sector in the inner or outer alternative sector area in a zone; and a second step of assigning/re-assigning another alternative sector to the same alternative sector area as the inner or outer alternative sector area in the zone to which the preceding alternative sector is assigned/re-assigned if the assignment/re-assignment of another alternative sector is required after the assignment/re-assignment of the preceding alternative sector and another alternative sector has a predetermined relation to the preceding alternative sector.
In the alternative sector assignment/re-assignment method according to the present invention, the second step may be performed if a sector assigned/re-assigned to another alternative sector exists in the zone in which a sector assigned/re-assigned to the preceding alternative sector exists. Furthermore, according to the present invention, whether another alternative sector has a predetermined relation to the preceding alternative sector or not may be determined by comparing the address of the sector assigned/re-assigned to the preceding alternative sector with the address of the sector assigned/re-assigned to another alternative sector. Both of the physical and logical addresses may be used. Whether said another alternative sector has a predetermined relation to said preceding alternative sector or not may be determined based on the amount of time elapsed between the assignment/re-assignment of said preceding alternative sector and the time at which the assignment/re-assignment of said another alternative sector is required. That is, an address or time is used as an indication for determining whether data is a series of related items of data.
In order to take advantage of the above-described assignment/re-assignment of alternative sectors more effectively, the present invention provides a method for reading data from a recording disk having an alternative sector area in which a collection of alternative sectors is provided and non-defective sectors, the method comprising: a first step of accessing a preceding alternative sector storing data for which a read request is made to read said data; a second step of reading data from an alternative sector succeeding the preceding alternative sector during the rotational latency required for a magnetic head to access a non-defective sector storing the next data for which a read request is made; and a third step of accessing the non-defective sector to read data after the second step.
According to the data reading method of the present invention, during reading data from one alternative sector, data is read from another alternative sector. Thus, the method eliminates the need for performing a seek operation each time data is read from an alternative sector, thereby allowing data to be read from the alternative sectors faster.
The present invention is especially effective if the above-described alternative sector assignment/re-assignment method of the present invention is applied to the preceding alternative sector and the succeeding alternative sector in the same inner or outer alternative sector area in the same zone. That is, according to the alternative sector assignment/re-assignment method of the present invention, a plurality of alternative sectors storing a series of related items of data are adjacent to each other in the inner or outer area in a zone, thus allowing a data read operation from different sectors to be performed faster.
In the present invention, preferably the rotation time required for the magnetic head to reach the non-defective sector storing said next data for which the read request is made from the preceding alternative sector from which the data is read at the first step is compared with the seek time and if it is determined that the rotation time is not equivalent to said seek time, the above mentioned second step is performed.
The present invention provides a disk drive apparatus that performs the alternative sector assignment/re-assignment method described above. The disk drive apparatus according to the present invention comprises a disk recording medium being capable of random access and having an alternative sector area in which a group of alternative sectors are provided; a storage section for storing the position of an alternative sector assigned/re-assigned precedently; a determination section for determining whether the assignment/re-assignment of an alternative sector succeeding said preceding alternative sector is required within a predetermined time; and a directive section for assigning/re-assigning the succeeding alternative sector to the same alternative sector area in which the alternative sector the position of which is stored in the storage section exists if the determination section determines that the assignment/re-assignment of the succeeding alternative sector is required within the predetermined time.
The present invention also provides a disk drive apparatus comprising: a disk recording medium being capable of random access and having an alternative sector; a storage section for storing the address of an alternative sector assigned/re-assigned precedently; a determination section for determining whether the physical address of first defective sector causing the assignment/re-assignment of the preceding alternative sector is adjacent to the physical address of a second defective sector for which it is determined that assignment/re-assignment of an alternative sector is required after the assignment/re-assignment of the preceding alternative sector; and an assignment/re-assignment section for assigning/re-assigning the address of the alternative sector of the second defective sector so that the address is adjacent to the address stored in the storage section if the determination section determines that the physical address of said first defective sector and the physical address of the second defective sector are adjacent to each other.
Furthermore, the present invention provides a disk drive apparatus comprising: a disk recording medium being capable of random access and having an alternative sector; a storage section for storing the position of an alternative sector assigned/re-assigned precedently; a determination section for determining whether the logical address of a defective sector assigned/re-assigned to the preceding alternative sector is close to the logical address of a defective sector for which it is determined that assignment/re-assignment of an alternative sector is required after the preceding alternative sector; a directive section for assigning/re-assigning the defective sector for which it is determined that the assignment/re-assignment of an alternative sector to an alternative sector near the position of the alternative sector stored in the storage section if the determination section determines that the logical address of the defective sector assigned/re-assigned to the preceding alternative sector is close to the logical address of said defective sector for which it is determined that the assignment/re-assignment of the alternative sector is required.
Examples of a typical disk recording medium capable of random access in the disk drive apparatus of the present invention include a hard disk, flexible disk, and magneto-optical disk. Therefore, the present invention can be applied to a hard disk drive. However, this is just an example of the application of the present invention and does not limit the present invention.
Furthermore, the present invention provides a disk drive apparatus comprising a disk recording medium being capable of random access and having a non-defective sector and an alternative sector, read control means for controlling data reading from said disk recording medium, and a head for reading said data according to the read control means, wherein the read control means controls data reading so as to read data from a different alternative sector besides an alternative sector if a read instruction is issued for data stored in the alternative sector; and the data reading from the different alternative sector is performed until the head is no longer allowed to access a non-defective sector in which the next data to be read is stored.
In the disk drive apparatus, the disk recording medium has circumferentially separated zones, each of which having a different data storage capacity, and alternative sector areas consisting of a collection of alternative sectors on the inner and outer sides of each zone; the different alternative sector is assigned/re-assigned to the inner or outer alternative sector area in which the alternative sector exists.
The present invention described above may be effectively applied to audio-visual data reading or writing. Because a momentary performance decrease may lead to a momentary halt of a moving image or a sound skip, there is a strong demand for faster data reading from alternative sectors in the audio-visual data applications. To meet this demand, the present invention proposes an apparatus for reading and writing audio-visual data, comprising a hard disk which audio-visual data is read from and written on and employs a zone-bit-recording-scheme, a write control section for controlling writing audio-visual data on the hard disk, and a read control section for controlling reading audio-video data from the hard disk, wherein: the hard disk has an alternative sector area consisting of a collection of alternative sectors in each zone; the write control section performs the assignment/re-assignment of a succeeding alternative sector to the same alternative sector area as the assignment/re-assignment of a preceding alternative sector, if the assignment/re-assignment of a preceding alternative sector and the assignment/re-assignment of a preceding alternative sector arise and data to be written in said succeeding alternative sector and data written in said preceding alternative sector can be regarded as data constituting a sequence of audio-visual items of data; and the read control section issues an instruction to read the audio-visual data stored in the alternative sector by said preceding assignment/re-assignment besides the audio-visual data stored in the alternative sector by the succeeding assignment/re-assignment.